Field of the Invention
The present invention relates to a multistage gear transmission system suitable for a speed-change gear unit of a saddle-ride type vehicle or automobile.
Description of the Related Art
As a speed-change gear unit for such a type of vehicles, an automated manual transmission (AMT) mechanism or a dual-clutch transmission (DCT) mechanism capable of providing both excellent mechanical efficiency of a manual transmission and convenience of an automatic transmission is increasingly employed.
As the AMT or DCT gearshift mechanism for a motorcycle, various types of structures for transmitting an actuating force from a motor to a shift cam have been proposed. For example, in the technique of Japanese Laid-open Patent Publication No. 2015-10709, the power of the motor is decelerated by an actuator gear and is transmitted to rotate a shift cam drive plate through a shift arm and pin fixed to rotate in synchronization with a shift shaft. In addition, a hook portion of the shift cam plate and a pin portion of the shift cam plate rotating in synchronization with the shift cam are engaged with each other, so that the gearshift operation is performed by rotating the shift cam. Further, the shift shaft is returned to a neutral position by a return spring.
Patent Document 1: Japanese Laid-open Patent Publication No. 2015-10709
Patent Document 2: Japanese Laid-open Patent Publication No. 2010-260548
However, in the structure of Japanese Laid-open Patent Publication No. 2015-10709, an actuator motor or an actuator gear is simply installed in a gearshift mechanism of a manual transmission of the prior art. Therefore, the number of components or the weight significantly increases compared to a manual gearshift mechanism of the prior art. Similarly, in the structure discussed in Japanese Laid-open Patent Publication No. 2010-260548, an actuator, a worm gear, a shift shaft, and a link mechanism for connecting the shift shaft and the actuator are installed in the manual gearshift mechanism of the prior art. For this reason, the structure becomes complicated. Therefore, the size of the motor inevitably increases due to degradation of mechanical efficiency in addition to an increase of the number of components or the weight.